Downtown roadwork for steam pipes will continue, as new boiler gets set to turn on

  • The installation of the original underground steam pipes around the New Hampshire Statehouse, in 1938 or 1939. Courtesy

  • The installation of the original underground steam pipes around the New Hampshire Statehouse, in 1938 or 1939. Courtesy

  • Construction on Green Street in Concord continues on Thursday, April 20, 2017. A temporary heating system is being installed for some state and city buildings before Concord Steam shuts down. (ELIZABETH FRANTZ / Monitor staff) Elizabeth Frantz

  • Green Street in Concord is dug up right down the middle of the street as they work on a temporary steam generation system downtown after Concord Steam stopped producing steam in the downtown area. GEOFF FORESTER

Monitor staff
Published: 8/24/2019 3:30:12 PM

The State House will soon be getting its heat from the new boiler building that replaces defunct Concord Steam, although exactly when depends on how many more surprises are encountered while laying the steam pipes.

Surprises like rocks. Big rocks.

“We found some absolutely huge rocks. There was one at the State House … we had to get a flatbed to haul it away. There was another by the (New Hampshire) State Library, probably three cubic yards,” said Michael Connor, deputy commissioner of the state Department of Administrative Services, which is overseeing the project.

Connor said the boilers in the new building at the corner of School and Green streets could go online by early October. It will send steam through new underground pipes to the State House and State Library, two of the buildings that are keeping steam heat because too much damage would be done to historic structures by upgrading.

Once it is clear that the new boiler and new pipes are working, the temporary boiler installed last year in the parking lot of the Department of Justice building will be removed and the area will again be available for parking.

The new boiler will back-feed steam through some of the existing underground pipes that were used by the old Concord Steam system, heating the State House Annex until new pipes are installed to that building, Connor said.

Traffic in downtown Concord has been frequently rejiggered by the project, which included digging up roads to install natural gas pipes and also steam-heating pipes.

Most of the steam pipes are four inches in diameter, surrounded by a foot or more of insulation, with two-inch condensate pipes carrying the liquid of condensed steam back to the boiler house. Most are buried about three feet deep, although that can vary depending on what else is underneath the road.

“We’ve encountered lots of pipes that went nowhere, lots of telephone lines that went nowhere … gas lines that weren’t well marked,” Connor said.

No dinosaur bones or unexpected historical finds? “No, we didn’t run into any relics,” he said.

Work on School Street connecting the annex will take place early next year, demolishing the old underground pipe and installing new pipe. Everything should be finished by early next summer – well after the initial completion target of this October.

The private Concord Steam company provided heat to large parts of the city for eight decades before competition from natural gas drove it out of business in 2017. Most buildings – private or owned by the city or the state government – have switched to heating provided by natural gas from individual or shared boilers, although at least one uses wood pellet boilers.

Overall, state government had 26 buildings heated by Concord Steam, most of them in the Hugh Gallen state office complex.

(David Brooks can be reached at 369-3313 or dbrooks@cmonitor.com or on Twitter @GraniteGeek.)

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